ABSTRACT
A diffuser needs to break up the reflected wavefront. While this can be achieved by shaping a surface, it can also be done by changing the impedance of the surface. Indeed, Schroeder diffusers are often interpreted as being a surface with a spatially-varying impedance. In this chapter, variable impedance is achieved by patches of absorption and reflection. Unlike the Schroeder diffuser, these cannot be designed for minimum absorption. These surfaces are hybrids somewhere between pure absorbers and nonabsorbing diffusers. Partial absorption is inherent in the design while any reflected sound is dispersed.
